850 Interface 4 Serial Ports

[toddtmw]

I never had an 850 interface back in the day. I had one of those SIO devices with a little box that ended in a centronics port for my printer and I bought the Atari modem that did native SIO ports.

 

My question:

Why did the 850 have FOUR serial ports? What else besides a modem could you plug into them? And could you actually use more than one at a time? (If you had more than one phone line, could you hook up multiple modems and run a BBS that could handle more than one simultaneous session?

 

Thanks!

[Bill Lange]

You could plug in a Hayes Chronograph. You could interface with a HAM radio. You could hook up an old (now really old) teletype. You could basically hook up anything that communicated through RS-232 standard.

[toddtmw]

But. But. But.

 

It just seems like WAY overkill four ports!

 

Did anyone EVER actually use more than one or two back then?

 

Like I said, the 850 was out of my price range (or at least out of my priority list) back then...

 

Thanks!

[+DrVenkman]

I don’t recall the specifics (but I’m sure a search here would turn them up) ... But not all 4 ports on the 850 were “full” interfaces. I think only one or two had full RS-232C compatibility, while the rest were stripped of some lesser-used signals. I never had one either back in the Ferg, and even today I don’t - I do have an ICD P:R:Connection which I purchased as part of a big lot 15 years ago. Just a few months ago I remembered I had it and now put it to use interfacing with an early-00’s vintage Lantronix box that I have connected to my LAN. So my Atari can now connect to Telnet services and IP-based “BBS” systems.

 

Anyway, the P:R:Connection manual has a decent amount of information in it about what signals are necessary for true RS-232C compatibility and which ones can be stripped out for limited, specialized functionality. The P:R:Connection itself has two R: ports, with one main port and one secondary port with fewer signals.

[+kheller2]

I could be misremembering but not all four ports were equivalent.

[Bill Lange]

The 850 manual also has the following examples:

 

 

How many times did you use all four joystick ports on the Atari 400/800. Except for Mule and a few other games, four joystick ports were probably overkill as well.

[+David_P]

If it can be used to play MULE, by definition it is necessary

[ivop]

It just seems like WAY overkill four ports!

 

Did anyone EVER actually use more than one or two back then?

 

According to Rob Zdybel (ANTIC Podcast #184), the designer of the 850 was an avid model railroad collector and he actually designed it around his needs for controlling his model trains! That's why there are so many ports.

[sup8pdct]

Port1 has full complement of rs232 signals similar to 9pin pc type. ports 2 and 3 are same with reduced control signals. port 4 is setup to control a teletype printer with current loops.

 

james

[ricortes]

You kind of have to remember there weren't a lot of standards back then like USB. Serial printers were one of the ways to get compatibility between everything from CP/M to Atari. Everyone except for nerds HATED dot matrix printers. I recall some teachers at the time said turning in a paper printed on a dot matrix printer was going to get an automatic F. Wasn't uncommon to have multiple printers with a combination of dot matrix and daisy wheel. So you could have have two serial printers, a modem, and a spare port with an 850.

[Bill Lange]

Also, Votrax (maker of the SC-01-A chip found in the Alien Group Voice Box) also made a RS-232C Votrax Personal Speech System. You could easily have a modem on R1, a chronograph on R2, a speech synthesizer on R3 and a printer on R4. Not likely, but possible.

 

 

 

 

According to Rob Zdybel (ANTIC Podcast #184), the designer of the 850 was an avid model railroad collector and he actually designed it around his needs for controlling his model trains!

 

 

 

I'd love to see photos or video of an Atari 8-bit controlling a model train layout using the 850!

Edited July 13, 2017 by Bill Lange

[Kyle22]

I would also enjoy seeing that.

[576XE]

Hi there, friends!

 

Some years ago I've tried to connect HLK-RM04

(It's very cheap and they say that it's fully implemented WiFi to RS-232 interface)

to SIO2PC and unsuccessfully

I never had 850 interface.

Do I need it or something else to communicate with Atari normally?

 

ez

[thorfdbg]

Why did the 850 have FOUR serial ports? What else besides a modem could you plug into them? And could you actually use more than one at a time?

No, you could not use them simultaneously in concurrent mode. In "small block mode", you can send to multiple ports, but you cannot receive data.

 

The 850 had a very impractical design - in the sense that POKEY in the Atari does the decoding, and not the 850 itself.

[DavidMil]

Seems like I remember someone making a weather station using one or maybe two RS232 ports to communicate with the 850 over a couple of 50

foot speaker/phone wires. One 232 port was for the temperature and I'm not sure if the other was for wind speed or rain. Sorry, that about 34 or 35

years ago, and the RAM space in my head could use some serious replacements!

 

David

[rcamp48]

On 7/18/2017 at 1:31 AM, DavidMil said:

Seems like I remember someone making a weather station using one or maybe two RS232 ports to communicate with the 850 over a couple of 50

foot speaker/phone wires. One 232 port was for the temperature and I'm not sure if the other was for wind speed or rain. Sorry, that about 34 or 35

years ago, and the RAM space in my head could use some serious replacements!

 

David

Bump: Has anyone come up with a custom ROM to allow use of all 4 serial ports at the same time?

           Altirra now allows all 4 ports to be used in version 4.10

 

Russ

 

[_The Doctor__]

yes you can use each port, but not at the same time. This was explained at a super simple level in another thread. Firmware in the eprom can't make up for more needed hardware, At best with buffering and SIO port speeds being raised to a little over 2 times it's current speed you might handle 2 ports.

[Greg Lovekamp]

Had a Hayes Smartmodem on port 1 and a Teletype on port 4 back in early 80’s. I wish I had that Teletype today; it was pristine.

[rcamp48]

20 hours ago, _The Doctor__ said:

yes you can use each port, but not at the same time. This was explained at a super simple level in another thread. Firmware in the eprom can't make up for more needed hardware, At best with buffering and SIO port speeds being raised to a little over 2 times it's current speed you might handle 2 ports.

The best I can do now that Altirra has changed is run 4 machines, I do have 4 machines and I can pass information through networked and mapped drives, I used to be able to run up to 8 or more machines at the same time on the same machine, but Altirra has changed to being only able to run one instance at a time. But I will be able to run 4 separate machines on my network, and should have them all running by tomorrow night (right now I need more ethernet cables and another power bar, that I have to get from my office). One question Doc: Is Altirra able to run real modems ???? If so I may put two online..... as I have an ATA box and a pair of VOIP lines that are world wide toll free, and at least 3 56 K modems.

 

Russ

 

[_The Doctor__]

I think you need to read about Altirra some more, last I knew you could still run multiple instances of it.

[thorfdbg]

On 2/5/2023 at 4:59 PM, rcamp48 said:

Bump: Has anyone come up with a custom ROM to allow use of all 4 serial ports at the same time?

No, and as said above, this cannot work. The 850 does not actually decode any serial data when receiving it. All the 850 does is to sample the serial line of one of its input ports, and directly forward this data to Pokey. The serial-to-parallel conversion is done by Pokey, not the interface box. Thus, Pokey is running at the baud rate of the incoming data, and the 850 operates in "pass-through". Due to the limited sampling period, 9600 baud is the maximum the interface box supports. As decoding is actually done by the main system and not the 850, there is also no way how to receive data at more than one port.

 

For sending data in concurrent mode, it is actually quite the same. All the 850 does is to sample the pokey output, and mirror it at one of its ports. The only mode within which the 850 actually uses its internal shift register is the "small block mode" within which pokey communicates to the 850 in full speed (19200 baud), and the 850 converts it to the target baud rate.